811820 has 12 divisors (see below), whose sum is σ = 1704864. Its totient is φ = 324720.

The previous prime is 811819. The next prime is 811861. The reversal of 811820 is 28118.

It is a Harshad number since it is a multiple of its sum of digits (20), and also a Moran number because the ratio is a prime number: 40591 = 811820 / (8 + 1 + 1 + 8 + 2 + 0).

It is a plaindrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 811792 and 811801.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20276 + ... + 20315.

It is an arithmetic number, because the mean of its divisors is an integer number (142072).

2⁸¹¹⁸²⁰ is an apocalyptic number.

It is an amenable number.

811820 is an abundant number, since it is smaller than the sum of its proper divisors (893044).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

811820 is a wasteful number, since it uses less digits than its factorization.

811820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40600 (or 40598 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 20.

The square root of 811820 is about 901.0105437785. The cubic root of 811820 is about 93.2867397821.

Adding to 811820 its reverse (28118), we get a palindrome (839938).

The spelling of 811820 in words is "eight hundred eleven thousand, eight hundred twenty".